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Chemical equations are like the language used to describe chemical reactions. They are written statements that use chemical symbols to communicate what happens when substances interact. A chemical equation consists of the reactants on the left side and the products on the right side, with an arrow pointing from reactants to products to indicate the direction of the reaction.

When writing a chemical equation, it's crucial to ensure it's balanced. Balancing means that the number of each type of atom on the reactant side must equal the number on the product side. This is because atoms cannot be created or destroyed in a chemical reaction. For instance, the equation for the reaction between hydrogen and oxygen to form water looks like this:
\[ 2H_2 + O_2 \rightarrow 2H_2O \].

Here, you see there are 4 hydrogen atoms and 2 oxygen atoms both before and after the reaction. Balancing chemical equations is important for accurately representing the chemical change and predicting the quantities of reactants needed or products formed.

In any chemical reaction, there are starting materials called 'reactants' and new materials formed known as 'products'. Reactants are the substances you begin with, and products are the substances you end up with after the reaction has taken place. For example, in the reaction of vinegar with baking soda, vinegar and baking soda are the reactants, while carbon dioxide, water, and sodium acetate are the products.

Understanding reactants and products is fundamental to chemistry because it tells you what changes are occurring. To identify them in a chemical equation, just look on either side of the arrow:

• Reactants appear on the left side of the equation.
• Products appear on the right side.

Knowing the reactants and products helps scientists know more about the reaction, such as what kind of reaction it is—whether it involves energy release or absorption—and how it might be useful in real-world applications.

The conservation of mass is a fundamental principle in chemistry which states that mass is neither created nor destroyed in a chemical reaction. This principle is why chemical equations must be balanced. During a reaction, the total mass of the reactants equals the total mass of the products.

This idea dates back to Antoine Lavoisier in the 18th century, who stated that matter can transform from one form to another but cannot simply vanish. This is why in a chemical equation, you must ensure that the number of atoms for each element is the same on both sides. For example, if a chemical equation shows an imbalance, it means there has been an error in the representation of the reaction.

To check conservation of mass, list all the elements involved and count their atoms on both sides of the equation. If these numbers match, the equation obeys the conservation of mass. This principle is critical in predicting the results and quantities of chemical reactions in laboratory settings and industrial applications.